I've been taking it for about two years, often skipping it on days I don't have to work, and it's definitely not as effective. Once, though, I did lose about three weeks' worth when it got accidentally tossed during a move. Insurance doesn't tend to cover that sort of thing, and the stuff is $500+/month, so I just struggled without. When I refilled it and started taking it again, I was bouncing off the walls a little bit.